In Inner Mongolia area in China, there is a mobile sand dune area that drifts and expands by the strong wind. The sand dune area is a typical example of the places where the ground surface is extensively covered with sand, such as desert areas, sand dunes, and beaches, and where the sand drifts on a massive scale by the force of the wind and the like. The desertification in this area is said to progress by such factors as the overgrazing of Cashmere goats or sheep as well as the encroaching sand that buries the plants. The sand is accused to be the cause of the sand dust that did damage to the near-by villages and the coastal areas of China, and to be the cause of the yellow sand phenomenon in South Korea and Japan. Not only people living in China, but also those in Japan are now calling for the lessening of the damage caused by the sand blown up from the mobile dune area.
Inner Mongolia area has a high precipitation for a desert region, and as a result has a high groundwater level. So, the greening of this area is considered to be possible if the sand near the ground surface is prevented from being moved by the strong wind and is thus fixed. What is called a straw checkerboard has been employed as a time-honored means of carrying out the greening.
The greening method called the straw checkerboard method is a sand controlling method using straw. In the method, firstly, lines are drawn in a grid pattern with intervals of, for example, one meter, on the surface of sandy soil. Then, the soil is shoveled to form grooves along the grid-patterned lines. After that, straw and the like are set up in the grooves while the bare-ground parts inside the grid lines are seeded. Accordingly, a state where the sand is more difficult to drift when viewed in totality can be accomplished and, in addition, the sandy soil can be converted into grassy pastures. The straw and the like, however, are not obtained easily. In addition, transporting the bulky straw and the like to the venue is difficult (note the necessity of transportation on the sandy soil). Moreover, the straw and the like deteriorate, so that replacement is needed every two or three years. In other words, there is a problem concerning the maintenance and the management after the setting up of the straw checkerboard.
A method in which used tires, arranged appropriately, are buried and fixed in the ground (see Patent Document 1, for example) is an example of methods of preventing the soil from flowing out and the like. Another example of the kind is a method in which sandbags having a certain structure and made of a certain material are fixed on the ground and linked together (see Patent Document 2, for example). Though methods, including these described above, have been proposed thus far, we have not yet discovered a method of efficiently fixing sand in a vast mobile sand dune area or in a sand dune.
Nor have we discovered yet a method of efficiently fixing sand in a vast mobile sand dune area or in a sand dune and thus greening the land efficiently.
Patent Document 1: Japanese patent application Kokai publication No. 2000-34709
Patent Document 2: Japanese patent application Kokai publication No. 2005-68832